Rejoin as and when its possible...don't keep a gap in rejoining such that u do not meet 2.5 years of articleship completion criteria to give ur first attempt whenever it will fall due.
If you are considering a transfer, please make sure that there is no delay in rejoining the new firm as any intermittent time gap shall not be counted for the Articleship period. This might lead to postponement of your Final Exams. Also the Institute may require you to submit details of transfer.